1. Field of Invention
The invention relates to an optical disk drive system and, in particular, to an optical disk drive system with quasi-parallel tasking and a servo control method.
2. Related Art
In a general optical disk drive system, as shown in FIG. 1, it usually comprises an optical pickup head 201 for reproducing signals from an optical disk 1, an R/F unit 202 for equalizing and shaping the RF signals reproduced from the optical disk 1 by the optical pickup head 201, and a synchronization unit 205 for creating a clock signal whose phase is synchronized with the binary data outputted from the R/F unit 202. The disk drive system also comprises a digital signal processing (DSP) unit 203 for processing the binary data stream received from the R/F unit 202 in order to retrieve digital data using the synchronization clock, an MPEG decoder 204 for decoding the retrieved digital data to obtain original pictures or audio data, and a sled motor 210 for moving the optical pickup head 201. The disk drive system further comprises a spindle motor 211 for rotating the optical disk 1, a driving unit 207 for driving the sled motor 210 and spindle motor 211, and a servo unit 206 for controlling the optical pickup head 201 and driving unit 207. A microprocessor 208 supervises overall operations of servo unit 206 and DSP unit 203, and a memory 209 stores data necessary for the microprocessor 208.
In the optical disk drive system, when the optical disk 1 is inserted into a disk tray of the optical disk drive system, it is clamped by a clamping device for alignment. Then, controlled by the servo unit 206, the driving unit 207 provides electric current to rotate the spindle motor 211, and maintains the rotation velocity of the optical disk 1 constant, at about 2,500 rpm.
To reproduce signals recorded on the optical disk 1, the optical pickup head 201, with a laser diode LD and photo diodes PD installed therein, forms a laser beam spot on the recording layer of the optical disk 1 by irradiating a laser beam emitted from the laser diode LD. The laser beam reflected from the optical disk 1 is collected by the photo diodes PD and converted into electric signals. The R/F unit 202 equalizes and shapes the electric signals to produce binary data, and the DSP unit 203 performs the processing of the binary data. The synchronization clock necessary for the DSP unit 203, synchronized with the binary data from the R/F unit 202, is provided by the synchronization unit 205.
The basic role of the sled motor 210 is to move the optical pickup head 201 in the radial direction. Controlled by the servo unit 206, the sled motor 210 moves the optical pickup head 201 rapidly in the radial direction in the track search mode for locating a desired track. If the track search mode is set by a user's request, the microprocessor 208 detects the position of the track which the optical pickup head 201 is currently accessing, calculates the distance between the present track and destination track, and issues a command to move the optical pickup head 201 to the destination track by jumping the calculated distance.
As shown in FIG. 2, the conventional microprocessor 208 may firstly perform a decode/interface procedure for receiving and decoding the instruction set by the user's request, so as to generate a procedure state, which represents the user's request (Step S01). Then, the microprocessor 208 performs a servo control procedure for generating a command (Step S02). Thus, the servo unit 206 can be controlled according to the issued command. At this point, the microprocessor 208 would not perform or execute other procedure unless the servo unit 206 returns the operation result according to the command. However, the waiting time of the microprocessor 208 results a waste of the microprocessor performance.
It is therefore a subjective of the invention to provide an optical disk drive system, which can solve the above-mentioned problems, for manufacturers and users.